The Chronic Kidney Disease in Children Study (CKiD) is a multi-center, prospective cohort study of children aged 1 to 16 years with mild to moderately impaired kidney function at study entry. Two clinical coordinating centers (CCCs) (at the Children's Hospital of Philadelphia (CHOP), and Children's Mercy Hospital (CMH) in Kansas City), a central laboratory (at the University of Rochester), and a data coordinating center (at Johns Hopkins Bloomberg School of Public Health) have formed a cooperative agreement to conduct this prospective study of chronic kidney disease in children. Since its inception in 2003, the scientific aims of CKiD have been to determine the risk factors for decline in kidney function and the effects of kidney function decline on risk factors for cardiovascular disease; growth failure and its associated morbidity; and neurocognitive function and behavior. The purpose of this application is to request funds to continue the cohort study from August, 2013 to July, 2018. The aims of the current proposal are to assess and improve the accuracy and precision of the CKiD estimating formulas in youth with early CKD, to define the risk of kidney disease progression in children according to the Kidney Disease Improving Global Outcomes (KDIGO) classification of CKD according to Cause, GFR and level of albuminuria, to define risk factors for accelerated and non-linear decline in GFR among strata of children with glomerular compared to non-glomerular diagnoses and in African Americans, and to assess physical performance, arterial stiffness and myocardial structure and function as GFR declines. The Midwest Clinical Coordinating Center Principal Investigator has clinical expertise in kidney disease in children, clinical research design, recruitment and retention, quality control of study procedures, and organization of collaboration across the multiple participating sites in CKiD. The CKiD study encompasses a geographically and racially diverse cohort. The structure of CKiD and its support of ancillary studies continue to stimulate novel approaches to identify risk factors for kidney disease progression. The infrastructure of CKiD continues to serve as a platform for career development awards for junior investigators and ancillary R01's for more senior colleagues. With longer follow-up and additional recruitment of subjects with mild kidney dysfunction and glomerular disease, we will continue to characterize novel biomarkers of kidney injury that are associated with CKD progression and its sequellae to inform future therapeutic trials.